So if an older man is having sex with a younger woman and also fronting her some money to cover the rent and her Beemer, that's prostitution? Awful lot of guys and their GFs are in jeopardy if that's the case. There is another legal angle. Under IRS rules, if you donate over a specified amount, I believe it is $11k a year, to someone, you have to file a gift tax return and pay (steep) taxes on it. There was one case I recall just like this sugar daddy situation, and the guy claimed he was not making gifts but paying for prostituion and therefore didn't owe any gift tax. Of course, then the Gf would be in trouble for not paying income taxes on the money. As i recall, the IRS ruled that you couldn't avoid gift tax by claiming payment for an illegal service.